Hydrocarbon Identification During Drilling Operation in Lampake Wells Using Advanced Gas Data: A Case Study

Sinaga, Iranta Bona, Umi Kurniyati, VICO Indonesia, Jakarta, Indonesia

The identification of reservoir formation fluids that is influenced by pressure, mud weight and mud type during drilling operation is often ambiguous. In matters of pay zone recognition, hydrocarbon-bearing reservoir as well as high or low-pressure formation need to be clearly detected. Knowing the composition of the formation fluid while drilling would be obviously one of the most useful data item. Analysis of gas shows extracted from the mud can provide a good indication of the formation fluids. The measurement contained in the mud should be reliable, sensitive at very low concentration and accurate enough to be interpreted.

The traditional gas chromatograph known as FID (Flame Ionization Detector) has been utilized as the primary tool for the last 16 years in VICO Indonesia. In 2002, in alignment with Drilling Campaign in Lampake Field, an advanced gas detection system has been successful­ly utilized and evaluated. The fully computerized gas detection system combines total gas and chromatographic measurements and has quicker cycling time for measuring in parts-per-mil-lion the concentration of alkane carbon molecules and molecular isomers. This advanced gas detection shows a continuous data stream with far more data points per interval and greater resolution due to a 42 seconds sampling time per complete chromatograph cycle.

The new gas ratio algorithm curves when utilizing the higher resolution chromatograph data set can lead to the identification of most reservoirs fluids during drilling phase. The new gas ratio curves initiated by Geoservices are labeled LH (light to heavy), MH (medium to heavy) and LM (light to medium) to compare various combinations of chromatographic components C1 through C5.